Many biopsy surgical appliances are currently known. They substantially include a needle made up of a thin probe ending with a stylet arranged coaxially inside a hollow circular element acting as a cannula, and a control device for needle operation.
With reference to patent U.S. Pat. No. 4,958,625, no device includes two sliders, aligned on the same needle axis, elastically loadable through a respective spring, and wherein a first slider carries the stylet and the other slider carries the cannula.
Such sliders are associated with hooking/releasing holding devices capable of keeping the same sliders in the wound or axial load position in order to be able to carry out, through controls, two different executions of the removal, namely, a first execution wherein said stylet slider and the cannula slider are released in quick sequence by a single control respectively. The second execution is one in which the stylet slider is released by a first control and the cannula slider is released by a second control.
More particularly, the above mentioned device envisages that hooking/releasing holding means of cannula slider are associated with, and/or co-operating with, the stylet slider, where releasing of the cannula slider holding means occurs and may occur when the stylet slider has reached the end of its advancement stroke only.
This technique presents some substantial drawbacks which vary according to the type of removal to be carried out mentioned hereinafter.
With reference to the first type of removal, that is the one in which the stylet and cannula are advanced in quick sequence, sometimes, in case of a particularly resistant tissue, there may be the inconvenience that execution of the removal is not performed correctly since the stylet slider, not reaching advancement limit stop, does not exert the pressure on cannula slider holding means necessary for their release.
This particular malfunction may cause even serious damage to the patient since it is necessary to move the needle with the stylet partially fed and the cannula backed, that is moving the needle before cannula has made the cut of the sample inside the pierced tissue.
With reference to the second type of removal, that is the one comprising a first stylet advancement by a first control and then a second cannula advancement by a second control, sometimes, in the aforementioned case of particularly resistant tissue, there may be a drawback in that the operator shoots the stylet at first and then, when he presses the push-button for cannula, the release does not occur since the stylet slider, as mentioned above, is not in limit stop position.